ruby on rails- nested attributes for 'has_one' relationship

Question

I need some help concerning nested attributes in models with 'has_one' relationship.

Model Survey has 1 question Model Question has 1 answer

How do i build the 'answer' in the code below

def new
  @survey = Survey.new
   @survey.build_question # build one question
    @survey.question.answer.build #this part is not working

end

Please can anybody tell me how to build the answer as the code "@survey.question.answer.build" is not correct.

Many many thanks for your help

Andy Lindeman · Accepted Answer · 2011-01-17 15:07:58Z

2

You must build the answer on the newly created Question instance since it's not yet been saved.

@survey = Survey.new
@question = @survey.build_question
@answer = @question.build_answer
# ... at some point in the future
@survey.save

edited Jan 17, 2011 at 15:07

answered Jan 17, 2011 at 14:51

Andy Lindeman

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6 Comments

Kim Over a year ago

Hi, thanks a lot for the suggestion but '@survey.question.build' does not seem to work when there is a 'has_one' relationship between the models. I have to use the following format '@survey.build_question' otherwise i get the following error message 'undefined method `build' for nil:NilClass'

Kim Over a year ago

If i am to use --- @survey = Survey.new @question = @survey.build_question @answer = @question.answer.build, then how do i tackle the @answer part ?? :(

Kim Over a year ago

I mean '@answer = @question.answer.build' is now giving me the following error message 'undefined method `build' for nil:NilClass'

Kim Over a year ago

I got it --it should be '@answer = @question.build_answer'

Kim Over a year ago

Question and Answer are in a has_one/belongs_to relationship and i guess that's the reason i was getting an error for the 3rd line of code but using '@answer = @question.build_answer' seems to be doing the job :). Thanks a lot for your help

|

Andrew · Accepted Answer · 2011-01-17 15:12:30Z

1

@survey = Survey.new
@survey.question = Question.new
@survey.question.answer = Answer.new
@survey.question.answer = (whatever)
@survey.save!

(or just @survey.save if you don't want to see exceptions)

If you want to make it easier to access these as instance variables in your view you can assign any of them to a variable after you've created them, and the association will be maintained:

@question = @survey.question

It's up to you.

answered Jan 17, 2011 at 15:12

Andrew

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